A TIME-CORRECTOR DEVICE FOR 

ADJUSTING STREAMnOW REOORDS 

The first job in compiling streamflow data from 

streamflow charts is to mark storm rises and storm peaks, 

make corrections as necessary for time and stage height, and 

account for irregularities on the chart. Errors in the time 

scale can result from faulty clock operation, irregularities 

in chart take-up by the drum, or expansion of the paper. 

This note suggests a device for making rapid and accurate 

time corrections. 

In preparing streamflow records at the Hubbard Brook 

Experimental Forest in West Thornton, N.H., time corrections 

are made if the chart time is more than 15 minutes in error 

at the end of a 2-week period. On the Stevens A-35 chart, 

used at Hubbard Brook, corrections at storm rises and peaks 

can be made to 5 minutes. The usual procedure is to prorate 

the error backward from the end of the time period over the 

number of days of record. 

One method of doing this is to construct a small 

graph on the chart and mark off the time correction on the 

vertical scale and the days of record on the horizontal 

scale, as shown in figure 1. The following example illustrates this method. 

Data From Chart 

Chart time at end of period ...... 0910 

Actual time at end of period ..... 0945 

Error in chart time .......... 35 minutes slow 

Date record started .......... June 1, 1959 

Date record ended ........... June 15, 1959 

Number of days in period ....... '15 

 or ease in computation, the days in which the chart is started and stopped 

are counted as full days; therefore 15 days is considered the period. 
On the graph (fig. I), the junction of the vertical 

day line with the diagonal gives the 5-minute interval correction for that day. For example: if a storm peak occurred 

on June 5 at 1020 (chart time), 10 minutes should be added 

to this time; thus 1030 is the actual time of the storm peak. 

Or, if a storm rise occurred at 0520 (chart time) on June 11, 

the corrected time is 0545. Points that fall on the junction of the horizontal and diagonal line can be assigned to 

the interval above or below the line by arbitrary rule. 

DATES OF RECORD 

Figure 1. --Graph used for making time corrections. 

Although this method is satisfactory, it requires a 

separate graph for each time-scale correction, and if long 

continuous roll charts are used the graph is covered up during the course of marking and winding. 

An adjustable scale was designed to overcome these 

disadvantages. This device consists of a graph, permanently 

scribed on plexiglas, with adjustable arms for setting the 

most commonly-used time corrections (fig. 2). Note that the 

graph below the diagonal arm is similar to that shown in 

figure 1. 

Two arms are provided to allow time corrections to be 

made for 8-day and 15-day periods.2 The borders of the 

graph are etched to permit writing in dates of record and 

time adjustments. 

The operation of the time corrector is as follows 

(using the data given in the example and figure 1): Write 

2~trearnflow charts (Stevens A-35 type) at the Hubbard Brook Experimental 

Forest are checked once a week and changed every second week. 
Figure 2. --The time-corrector device. A, the graph, scribed 

on 1/16-inch plexiglas; B, the adjustable plexiglas arm for 

15-day period (reading edge on lower side); C, adjustable 

arm for 8-day period; D, pivot point (copper pin permanently 

set in plate and arm); E, ~et-~in (copper pin set in adjustable arm, engages hole in graph to position arm); F, positioning holes in graph; G, etched margins of graph for writing in dates of record and time adjustments. 

dates of record along the etched part of the graph below the 

bottom horizontal line. Rotate the long arm on the graph (B) 

until its lower edge forms a straight line from the pivot 

point to the intersection of the horizontal line between 35 

and 40 and the last vertical line to the right. Place the 

set-pin on the arm in its appropriate hole provided in the 

plexiglas plate. As in figure 1, a time correction for a 

storm peak on June 5 would involve a correction of 10 minutes, for June 11, 25 minutes. 

If corrections are desired for an 8-day period, the 

same procedure is followed, using the short arm (C). 
This device can be adapted for making time corrections for precipitation intensity and hygro-thermograph 

charts, and also for correcting any prorated error such as 

gage height and skew.3 

--RAYMOND W. LAVIGNE 

Northeastern Forest Experiment Station 

Laconia Research Center 

Laconia, N.H. 

3~kew occurs when the chart is incorrectly ~ositioned on the drumj i. e., the 

horizontal lines on the chart are not parallel to the drum rim.